Python Forum

Can anyone tell me how I can save a Matplotlib chart to a temporary file I create using

tempfile.NamedTemporaryFile()

?

I can't use the Matplotlib's default savefig('hardcoded_file_path') method since I'm in a REST service and I need to control the path so I can delete the temp file when done.

Thank you in advance.

import random
import os
from tempfile import NamedTemporaryFile

import matplotlib.pyplot as plt
from PIL import Image


plt.hist([random.random() for _ in range(100)])
with NamedTemporaryFile("r+b", delete=True) as fd:
    # delete is by default True
    # the if you don't set it, it will delete the file
    # after leaving the with block
    plt.savefig(fd)
    # seeking back to position 0
    # allowed by r+
    fd.seek(0)
    # show the image from temporary file with PILLOW
    Image.open(fd).show()
    # Image is shown (window opens)
    # but then directly the block is left and the NamedTemporaryFile is deleted

print(fd.name, end=" ")
if os.path.exists(fd.name):
    print("still exists.")
else:
    print("was deleted.")

You should read the documentation of NamedTemporaryFile.

Edit:
plt.savefig first argument could be a str or path-like object or a file-like object.

fname : str or path-like or binary file-like
    A path, or a Python file-like object, or
    possibly some backend-dependent object such as
    `matplotlib.backends.backend_pdf.PdfPages`.

This allows also the use of FakeFiles like io.BytesIO.

import random
import io

import matplotlib.pyplot as plt
from PIL import Image


plt.hist([random.random() for _ in range(100)])
file_like = io.BytesIO()
plt.savefig(file_like)
file_like.seek(0)
Image.open(file_like).show()

Thanks so much! :)

Morkus

DeaD_EyE

Morkus